I'm from Brazil and I have the same issue, mic doesn't work fine when using the speaker at a call and one side of the stereo sound at recordings is 90% lower than the other side, also reccording programs like whatsapp or skype ain't working aswell.
We also have a topic at the Brazilian Nokia Comunitty about this issue and we have around 100~120ppl with the same issue, seems it's a generic problem and microsoft/nokia ain't doing nothing about it. Sad :(